1. Field of the Invention
The present invention relates to a stack-type piezoelectric device used as a drive source in control of a valve of a micropump or the like.
2. Related Background Art
An example of the conventional stack-type piezoelectric devices is the one described in Japanese Patent Application Laid-Open No. 2002-254634. This stack-type piezoelectric device has an active layer consisting of an alternate stack of piezoelectric layers in each of which a number of individual electrodes are formed, and piezoelectric layers in each of which a common electrode is formed. This active layer is displaced in the stack direction when a voltage is applied between the individual electrodes and the common electrodes. A layer laid at one end in the stack direction is a piezoelectric layer in which a number of terminal electrodes for applying the voltage between the individual electrodes and the common electrodes are formed.
In the stack-type piezoelectric device of this type, a driven object such as a valve of a micropump is attached to a piezoelectric layer at the other end in the stack direction. When the voltage is applied through the terminal electrodes between a plurality of individual electrodes aligned in the stack direction and the common electrodes, active parts corresponding to the plurality of individual electrodes in the active layer (portions to be distorted by piezoelectric effect in the piezoelectric layers) are displaced in the stack direction to actuate the driven object.
For this reason, it is important to securely transmit the displacement of the active layer to the other end side in the stack direction (i.e., the side where the driven object is to be attached) and, for implementing it, there are cases where an inactive layer is laid between the active layer with the internal electrodes such as the individual electrodes and the common electrodes, and the piezoelectric layer with the terminal electrodes.